Annual Phytoplankton Biomass Cycles Research Articles

Variability of phytoplankton biomass and environmental drivers in a semi-enclosed coastal ecosystem (San Matías Gulf, Patagonian Continental Shelf, Argentina) using ocean color remote sensing (MODIS) and oceanographic field data: Implications for fishery resources

Annual cycles of phytoplankton biomass (using chlorophyll-a as a proxy) and seasonal patterns of environmental drivers were analyzed in a semi-enclosed coastal ecosystem (San Matías Gulf, SMG, Patagonian Continental Shelf, Argentina). Monthly climatologies (2003–2014) of satellite images of chlorophyll-a (Chla-sat), sea surface temperature (SST), photosynthetically available radiation (PAR), and euphotic depth (Z 1% ) were analyzed using Principal Component Analysis (PCA). Satellite environmental variables were evaluated together with oceanographic field data (temperature, nitrate, and chlorophyll-a). Thus, this study analyzes the Chla-sat data to describe the spatio-temporal distribution of the phytoplankton biomass in the SMG and investigates its relationship with the regional environmental drivers. Two contrasting phytoplankton annual cycles characteristic of these temperate waters were distinguished. PCA discriminated the inner and outer areas separated by a complex frontal system. The gulf's inner waters showed a bimodal phytoplankton cycle (maximums in autumn and spring) associated with the seasonal stratification of the water column in deeper areas and the consequent nitrate limitation in summer. The outer waters adjacent to the continental shelf showed unimodal cycles (maximum in autumn or spring) linked to the vertical mixing of the water column in shallow areas with moderate light intensity and nitrate availability. For both annual phytoplankton cycles, light is the main limiting factor in winter. Finally, the analyzed environmental patterns suggest that a tidal front favor feeding and spawning fishery resources in the north of the gulf. • Twelve years of chlorophyll-a MODIS data are analyzed in San Matías Gulf. • Environmental data from satellite and oceanographic cruises are investigated. • A frontal system separated two contrasting annual cycles of phytoplankton biomass. • Oceanographic features are favorable for feeding and spawning of fisheries resources.

Пространственно-временная изменчивость концентрации хлорофилла «а» в Краснодарском водохранилище по данным спутниковых снимков

The Krasnodar Reservoir has undergone significant transformations during its operation since 1973. As a result, of active delta formation of the Kuban and Belaya rivers, the reservoir was divided into two autonomous reservoirs, its area decreased by 35 %. The study is aimed at determining the significance of the eutrophication factor in the transformation of the Krasnodar Reservoir. Methods. Based on 51 Sentinel-2 satellite images for 2015–2020 the results of calculations of the concentration of chlorophyll «a» as an indicator of phytoplankton biomass in the reservoir are presented. The MSI sensor calculates the concentration of chlorophyll a (chl «a») based on the normalized chlorophyll difference index. Chl «a» estimates were obtained for a total area of 277 km2; the main bowl of the Krasnodar Reservoir and the Tshchik Reservoir, which was cut off from it. We have built maps reflecting the spatial and intra-annual variability of chl «a». Results The highest average concentrations of chl «a» are characteristic of the shallow upper part of the Krasnodar Reservoir, which is influenced by the runoff of the Kuban and Pshish rivers with an increased nutrient content. Locally high average values of chl «a» were recorded in the areas of the runoff current and in the estuaries of the left-bank tributaries. In the Tshchik water body with a low intensity of water exchange, the relationship between the concentration of chl «a» and hydrodynamic processes is not evident. We have revealed features of the annual cycle of phytoplankton biomass. It has been established that the trophic status of the reservoir is subject to seasonal variability: in spring, 2/3 of the water area correspond to eutrophic waters, 1/3 to mesotrophic waters; in autumn, the entire reservoir has a eutrophic status.

Seasonal modulation of phytoplankton biomass in the Southern Ocean

Over the last ten years, satellite and geographically constrained in situ observations largely focused on the northern hemisphere have suggested that annual phytoplankton biomass cycles cannot be fully understood from environmental properties controlling phytoplankton division rates (e.g., nutrients and light), as they omit the role of ecological and environmental loss processes (e.g., grazing, viruses, sinking). Here, we use multi-year observations from a very large array of robotic drifting floats in the Southern Ocean to determine key factors governing phytoplankton biomass dynamics over the annual cycle. Our analysis reveals seasonal phytoplankton accumulation (‘blooming’) events occurring during periods of declining modeled division rates, an observation that highlights the importance of loss processes in dictating the evolution of the seasonal cycle in biomass. In the open Southern Ocean, the spring bloom magnitude is found to be greatest in areas with high dissolved iron concentrations, consistent with iron being a well-established primary limiting nutrient in this region. Under ice observations show that biomass starts increasing in early winter, well before sea ice begins to retreat. The average theoretical sensitivity of the Southern Ocean to potential changes in seasonal nutrient and light availability suggests that a 10% change in phytoplankton division rate may be associated with a 50% reduction in mean bloom magnitude and annual primary productivity, assuming simple changes in the seasonal magnitude of phytoplankton division rates. Overall, our results highlight the importance of quantifying and accounting for both division and loss processes when modeling future changes in phytoplankton biomass cycles.

Student's tutorial on bloom hypotheses in the context of phytoplankton annual cycles

Phytoplankton blooms are elements in repeating annual cycles of phytoplankton biomass and they have significant ecological and biogeochemical consequences. Temporal changes in phytoplankton biomass are governed by complex predator–prey interactions and physically driven variations in upper water column growth conditions (light, nutrient, and temperature). Understanding these dependencies is fundamental to assess future change in bloom frequency, duration, and magnitude and thus represents a quintessential challenge in global change biology. A variety of contrasting hypotheses have emerged in the literature to explain phytoplankton blooms, but over time the basic tenets of these hypotheses have become unclear. Here, we provide a “tutorial” on the development of these concepts and the fundamental elements distinguishing each hypothesis. The intent of this tutorial is to provide a useful background and set of tools for reading the bloom literature and to give some suggestions for future studies. Our tutorial is written for “students” at all stages of their career. We hope it is equally useful and interesting to those with only a cursory interest in blooms as those deeply immersed in the challenge of understanding the temporal dynamics of phytoplankton biomass and predicting its future change.

Polar merry-go-round

The dynamics of polar marine ecosystems are poorly understood. A laser-based space-borne sensor captures annual cycles of phytoplankton biomass in seasonally ice-free polar waters, and provides clues on how growth drives these cycles.

Annual cycles of phytoplankton biomass in the subarctic Atlantic and Pacific Ocean

AbstractHigh‐latitude phytoplankton blooms support productive fisheries and play an important role in oceanic uptake of atmospheric carbon dioxide. In the subarctic North Atlantic Ocean, blooms are a recurrent feature each year, while in the eastern subarctic Pacific only small changes in chlorophyll (Chl) are seen over the annual cycle. Here we show that when evaluated using phytoplankton carbon biomass (Cphyto) rather than Chl, an annual bloom in the North Pacific is evident and can even rival blooms observed in the North Atlantic. The annual increase in subarctic Pacific phytoplankton biomass is not readily observed in the Chl record because it is paralleled by light‐ and nutrient‐driven decreases in cellular pigment levels (Cphyto:Chl). Specifically, photoacclimation and iron stress effects on Cphyto:Chl oppose the biomass increase, leading to only modest changes in bulk Chl. The magnitude of the photoacclimation effect is quantified using descriptors of the near‐surface light environment and a photophysiological model. Iron stress effects are diagnosed from satellite chlorophyll fluorescence data. Lastly, we show that biomass accumulation in the Pacific is slower than that in the Atlantic but is closely tied to similar levels of seasonal nutrient uptake in both basins. Annual cycles of satellite‐derived Chl and Cphyto are reproduced by in situ autonomous profiling floats. These results contradict the long‐standing paradigm that environmental conditions prevent phytoplankton accumulation in the subarctic Northeast Pacific and suggest a greater seasonal decoupling between phytoplankton growth and losses than traditionally implied. Further, our results highlight the role of physiological processes in shaping bulk properties, such as Chl, and their interpretation in studies of ocean ecosystem dynamics and climate change.

Comparison of surface chlorophyll, primary production, and satellite imagery in hydrographically different sounds off southern New England

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 535:29-45 (2015) - DOI: https://doi.org/10.3354/meps11386 Comparison of surface chlorophyll, primary production, and satellite imagery in hydrographically different sounds off southern New England Lindsey Fields1,5,*, Jeffrey Mercer1, Kimberly J. W. Hyde2, Mark Brush3, Scott W. Nixon1, Candace Oviatt1, Malia L. Schwartz4, David Ullman1, Daniel Codiga1 1Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA 2NOAA/NMFS, Narragansett, RI 02882, USA 3Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Point, VA 23062, USA 4University of Rhode Island, Kingston, RI 02881, USA 5Present address: Department of Marine Sciences, University of Georgia, 325 Sanford Drive, Athens, GA 30602, USA *Corresponding author: lfields@uga.edu ABSTRACT: Block Island Sound (BIS) and Rhode Island Sound (RIS) are adjacent inner continental shelf ecosystems with contrasting hydrographic regimes. BIS exhibits more energetic tidal mixing, and water column stratification remains weak but persists year-round due to nearby estuarine exchange flow; RIS is less influenced by estuaries, and more seasonal with strong stratification in summer. We compared annual cycles of phytoplankton biomass and primary production in BIS and RIS using measurements (surface chlorophyll, 14C primary production), primary production models (Webb/Platt and BZE models), and satellite ocean color products. During 22 mo of sampling, measured surface chlorophyll was not significantly different between BIS (mean = 1.86 mg m-3) and RIS (1.69 mg m-3), and bimodal peaks of phytoplankton biomass and production occurred concurrently in both Sounds. In contrast, a 12 yr ocean-color based chlorophyll time series indicated higher long-term average surface chlorophyll in the more well-mixed system (BIS, mean = 1.50 mg m-3; RIS, mean = 0.86 mg m-3). BIS annual primary production (318 to 329 g C m-2 yr-1) was higher than RIS (239 to 256 g C m-2 yr-1; p < 0.001). These differences were most apparent during the summer, concurrent with the largest differences in water column stratification. Phytoplankton bloom phenology was driven by physical processes, with chlorophyll significantly related to water column stratification (r = -0.51, p = 0.01), depth of the euphotic zone (r = -0.54, p = 0.05), and surface water salinity (r = 0.54, p = 0.04). Primary production was correlated with surface water temperature (r = 0.57, p = 0.03) but the mechanisms underlying production differences between the Sounds remain unresolved. We hypothesize that different hydrographies give rise to different productivity between the Sounds. KEY WORDS: Chlorophyll a · Primary production · Continental shelf · Stratification · Remote sensing · Empirical model Full text in pdf format PreviousNextCite this article as: Fields L, Mercer J, Hyde KJW, Brush M and others (2015) Comparison of surface chlorophyll, primary production, and satellite imagery in hydrographically different sounds off southern New England. Mar Ecol Prog Ser 535:29-45. https://doi.org/10.3354/meps11386 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 535. Online publication date: September 15, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Spring blooms and annual cycles of phytoplankton: a unified perspective

Several hypotheses exist that describe phytoplankton spring blooms in temperate and subpolar oceans: the critical depth, shoaling mixed layer (ML), critical turbulence, onset of stratification and disturbance-recovery hypotheses. These theories appear to be mutually exclusive and none of them describe the annual cycle of phytoplankton biomass. Here, we present a model of the annual cycle in phytoplankton that recognizes that phytoplankton are not always mixed throughout the so-called ML, and that it is important to distinguish between the surface biomass and depth-integrated phytoplankton. Once these important distinctions are made, the annual cycles and blooms in surface and depth-integrated phytoplankton can be described straightforwardly in terms of the physical drivers and biotic responses.

Downscaling the marine modelling effort: Development, application and assessment of a 3D ecosystem model implemented in a small coastal area

The present study deals with the development, application and evaluation of a modelling tool, implemented along with a field sampling program, in a limited coastal area in the Northeast Aegean. The aim was to study, understand and quantify physical circulation and water column ecological processes in a high resolution simulation of a past annual cycle. The marine ecosystem model consists of a three dimensional hydrodynamic component suitable for coastal areas (Princeton Ocean Model) coupled to a simple ecological model of five variables, namely, phytoplankton, nitrate, ammonia, phosphate and dissolved organic carbon concentrations. The ecological parameters (e.g. half saturation constants and maximum uptake rates for nutrients) were calibrated using a specially developed automated procedure. Model errors were evaluated using qualitative, graphic techniques and were quantified with a number of goodness-of-fit measures. Regarding physical variables, the goodness-of-fit of model to field data varied from fairly to quite good. Indicatively, the cost function, expressed as mean value per sampling station, ranged from 0.15 to 0.23 for temperature and 0.81 to 3.70 for current speed. The annual cycle of phytoplankton biomass was simulated with sufficient accuracy (e.g. mean cost function ranging from 0.49 to 2.67), partly attributed to the adequate reproduction of the dynamics of growth limiting nutrients, nitrate, ammonia and the main limiting nutrient, phosphate, whose mean cost function ranged from 0.97 to 1.88. Model results and field data provided insight to physical processes such as the development of a wind-driven, coastal jet type of surface alongshore flow with a subsurface countercurrent flowing towards opposite direction and the formation of rotational flows in the embayments of the coastline when the offshore coastal current speed approaches values of about 0.1 m/s. The percentage of field measurements where the N:P ratio was found over 16:1 varied between stations from 57 to 65%, demonstrating the importance of phosphate as a limiting nutrient for phytoplankton growth. The model also successfully reproduced phytoplankton gradients, e.g. those developed almost all year round between the most eutrophic areas (city harbour with mean chlorophyll-a concentration of 1.08 μg/L and decreasing biomass by over 40 mg C/m3 from surface to the bottom layer) and the oligotrophic open waters (mean chlorophyll-a concentration of 0.14 μg/L).

Establishing a global climatology of marine phytoplankton phenological characteristics

The timing or phenology of the annual cycle of phytoplankton biomass can be monitored to better understand the underpinnings of the marine ecosystem and assess its response to environmental change. Ten‐year, global maps of the mean date of bloom onset, peak concentration and termination of bloom duration were constructed by extracting these phenological metrics from Generalized Linear Models (GLM) fit to time series of 1° × 1° daily estimates of SeaWiFS chlorophyll concentrations dating from September 1997 to December 2007 as well as to MODIS chlorophyll concentrations from July 2002 to July 2010. The fitted models quantitatively define the annual cycle of phytoplankton throughout the global ocean and from which a baseline of phenological characteristics was extracted. The analysis revealed regionally consistent patterns in the shape and timing of the annual cycle of chlorophyll concentration that are broadly consistent with other published studies. The results showed that a single bloom predominates over the global ocean with secondary, autumn blooms being limited in both location and spatial extent. Bloom duration tended to be zonally consistent, but meridionally complex and did not become progressively shorter with increasing latitude as is sometimes depicted. Both the shape of the annual cycle and the phenological climatologies can be used in future studies to detect significant departures over time.

The annual cycles of phytoplankton biomass

Terrestrial plants are powerful climate sentinels because their annual cycles of growth, reproduction and senescence are finely tuned to the annual climate cycle having a period of one year. Consistency in the seasonal phasing of terrestrial plant activity provides a relatively low-noise background from which phenological shifts can be detected and attributed to climate change. Here, we ask whether phytoplankton biomass also fluctuates over a consistent annual cycle in lake, estuarine-coastal and ocean ecosystems and whether there is a characteristic phenology of phytoplankton as a consistent phase and amplitude of variability. We compiled 125 time series of phytoplankton biomass (chlorophyll a concentration) from temperate and subtropical zones and used wavelet analysis to extract their dominant periods of variability and the recurrence strength at those periods. Fewer than half (48%) of the series had a dominant 12-month period of variability, commonly expressed as the canonical spring-bloom pattern. About 20 per cent had a dominant six-month period of variability, commonly expressed as the spring and autumn or winter and summer blooms of temperate lakes and oceans. These annual patterns varied in recurrence strength across sites, and did not persist over the full series duration at some sites. About a third of the series had no component of variability at either the six- or 12-month period, reflecting a series of irregular pulses of biomass. These findings show that there is high variability of annual phytoplankton cycles across ecosystems, and that climate-driven annual cycles can be obscured by other drivers of population variability, including human disturbance, aperiodic weather events and strong trophic coupling between phytoplankton and their consumers. Regulation of phytoplankton biomass by multiple processes operating at multiple time scales adds complexity to the challenge of detecting climate-driven trends in aquatic ecosystems where the noise to signal ratio is high.

Phenology of marine phytoplankton from satellite ocean color measurements

[1] Climate change is expected to affect the timing and magnitude of numerous environmental conditions, including temperature, wind, and precipitation. Amongst other repercussions, such alterations will engender a response in marine ecosystem productivity manifested by changes in the timing and magnitude of phytoplankton biomass and primary productivity. Several investigations have examined the change in magnitude in chlorophyll concentration in relation to changing environmental conditions, but little has been done to examine the change in the timing of the annual cycle of phytoplankton biomass. In order to establish a baseline from which to assess any future changes in the phenology of phytoplankton biomass, we constructed nine-year climatologies of phytoplankton bloom onset, maturity, start of bloom decay, and termination in the central North Atlantic. This was accomplished by extracting annual values of these phenological markers from Generalized Linear Models fit to pentad (five-day) estimates of SeaWiFS chlorophyll concentrations dating from 1998 to 2006. This novel modeling approach, which produced results consistent with known patterns of phytoplankton bloom dynamics in this region, provides a statistically robust approach to detect and account for changes in the annual cycle of phytoplankton biomass.

Is phytoplankton growth in the Wadden Sea light or nitrogen limited?

The growth of phytoplankton in the Wadden Sea, a shallow tidal sea bordering the North Sea, is strongly regulated by nutrients and irradiance. The similarity and unity of this sea is documented on the basis of the annual phytoplankton biomass cycles at different sites. Due to the large inputs of nutrients in this area by several rivers (Rhine, Ems, Weser, Elbe) the Wadden Sea shows signs of eutrophication. The strong preference for eutrophication-related studies in this area can only be explained by the impact of policy-makers through funding of eutrophication-related studies and their will to manage the inputs of nutrients to the Wadden Sea. This strong preference has caused the relatively little interest for studies on the regulatory mechanisms of underwater irradiance on phytoplankton growth in this turbid area. Procedures developed by Cloern [Aquat. Ecol. 33 (1999)] were used to compare nutrient and light limitation at different sites of the Wadden Sea. The analysis showed that in many cases both spatial and temporal light limitation far exceed effects of nutrient limitation. During the 1990s the dominant influence of high DIN concentrations implies that underwater irradiance by far exceeds effects of nutrients on the production of phytoplankton biomass. Results of this analysis also show how narrowly focussed research may develop when policy-makers direct research priorities.

An annual cycle of phytoplankton biomass in the Arabian Sea, 1994–1995, as determined by moored optical sensors

A surface-to-bottom mooring in the central Arabian Sea (15.53N, 61.53E) deployed from October 1994 to October 1995, included #uorometers, PAR irradiance sensors, Lu sensors, and a spectral radiometer. An annual cycle of phytoplankton biomass was determined by transforming signals from the optical sensors into chlorophyll a (chl a). Half-yearly phytoplankton blooms with water-column stratication were observed near the end of each monsoon, as well as biomass increases in response to mesoscale #ow features. During the Northeast Monsoon, the integrate water-column chl a rose from 15 to 25 mg m, while during the Southwest Monsoon, chl a increased from 15 to a maximum '40 mg m. We present an empirical relationship between the ratio of downwelling E 443/E 550 (blue to green wavelength ratio) and integral euphotic zone chl a determined by moored #uorometers (r0.73). There is a more signicant relationship between E 443/E 550 measured at one depth in the water column (65 m) and the average vertical attenuation coe$cient for PAR (K ) between 0 and 65 m (r0.845). Because biofouling was a signicant problem at times, data return from any one sensor was incomplete. However, optical sensor/data intercomparison helped ll gaps while permitting investigation of the temporal variability in observed phytoplankton biomass. 2001 Elsevier Science Ltd. All rights reserved.

Annual cycles of phytoplankton chlorophyll concentrations in the global ocean: A satellite view

Conceptual and mathematical models show that annual cycles of phytoplankton biomass are different within different regions of the ocean. The purpose of this manuscript is to use coastal zone color scanner chlorophyll imagery (CZCS‐Ch1) to determine annual cycles in phytoplankton chlorophyll (biomass) averaged over very large areas of the global ocean. A possible result is that large‐scale averaging of CZCS‐Ch1 will yield no interpretable signals because of spatial variability in annual cycles at scales much smaller than our averaging scale. Alternatively, if our analyses show regular and persistent global patterns, then our results will jprovide a basin‐scale overview of phytoplankton biomass seasonally for comparison with model results or with other large‐scale oceanographic measurements. Our results show that monthly mean CZCS‐Ch1 imagery (and using in situ concentrations for winter at latitudes poleward of 40 deg) resolves important differences in annual phytoplankton chlorophyll cycles for different ocean basins and latitude belts. As predicted by simple models of plankton dynamics, our results show: (1) global subtropical waters have circa 2X higher CZCS‐Ch1 concentrations in winter than in summer and (2) subpolar waters in the northern hemisphere (NH) have mean monthly CZCS‐Ch1 concentrations during May and June that are manyfold higher than in winter, particularly in the North Atlantic. Our results also show: (1) Northern Indian Ocean is the major subtropical anomaly, (2) subpolar waters in the SH do not show differences between spring maxima and winter minima as large as those in the subpolar NH and (3) larger ocean area in the SH is compensated by higher mean annual CZCS‐Ch1 concentrations in the NH, so that annual hemispherical integrals (mean annual concentrations multiplied by ocean areas) are very similar. The simple patterns we report imply that mean annual cycles in phytoplankton biomass averaged over very large areas of the global ocean are largely explainable by very simple mathematical models such as those presented several decades ago by Cushing, Riley, Steele, and others.

Usefulness of simultaneous use of several methods for the estimation of phytoplanktonic biomass

The annual cycle of phytoplankton biomass was followed in a eutrophic lake (Lake Aydat, Massif Central, France), using classic descriptors (biovolumes and chlorophyll a) as well as adenosine-5'-phosphate (ATP) levels. ATP is the metabolite indicating living biomass. ATP/Cell count and ATP/Chlorophyll a ratios were elevated due to the presence of heterotrophic organisms, such as several species of ciliates. The first ratio is greater than the second. The difference can be explained either by an underestimation of the nanoplankton fraction through the cell count method, or by a lack of sedimentation in the settling chambers used for counting cells.